Routine surveillance of the incidence of vaccine-preventable diseases has not proved sensitive enough to demonstrate the impact of the Expanded Programme on Immunization (EPI) in many countries. In order to document progress since the start of the EPI in 1979, data are needed for several years prior to that. In most developing countries these can be found only in major cities or large hospitals. Therefore a system of sentinel surveillance, the Local Area Monitoring Project (LAM), is being set up in selected institutions in the major cities of the developing world. The goal is to include the major city of each of the 25 largest developing countries, with a total population of 115 million. These 25 countries together account for 85% of all births in the developing world. In some cases the city was selected because it had an excellent municipal reporting system. For example, the Istanbul Health Office collects data from 169 hospitals, primary health centres, maternal and child health clinics and other institutions, and provides compiled municipal figures within six weeks. The trend of measles cases seen at the Children's Hospital exactly matches the trend for the city as a whole, indicating that for measles, at least, the Children's Hospital is an excellent sentinel site representative of the whole city. Manila has a hospital to which all cases of infectious disease are routinely referred, which is also a good sentinel site. In Rangoon it has been necessary to survey four hospitals, and in Jakarta seven, to cover all the target diseases. By the first half of 1987, 12 years of retrospective data from 5-12 cities (depending on the disease) had been collected. Reporting was most complete for poliomyelitis and measles (76-80% of cities reporting), least complete for tetanus and neonatal tetanus (20-28%). An attempt was made to assess the quality of the data from each sentinel site by reviewing the records for continuity, and comparing the number of cases of infectious disease with those expected or those found from other surveys. If the site was a hospital, the size of the population served had to be calculated in order to compute incidence rates, or else the total city population was used as a proxy. In order to compensate for variations between cities in the incidence rates, and to give each city equal weight in the analysis, the average of each city's percentage change from baseline (1974-1978) was used. Judging from this, for the cities concerned, there has been a 62% reduction in the incidence of reported poliomyelitis by 1985, a 61% reduction for neonatal tetanus, 59% for diphtheria, 39% for measles, 35% for pertussis, and a decrease fluctuating between 0% and 24% for tuberculosis. Measles vaccination was added late to many country immunization programmes; therefore, the decrease in incidence began later than for the other diseases. BCG vaccine has its greatest effect on the severe childhood forms of tuberculosis, but the sentinel institutions do not usually report separately childhood, miliary or meningeal disease, hence the lack of a demonstrable trend. For the other target diseases, sentinel-site surveillance is proving to be a useful method for measuring programme impact.
|Original language||English (US)|
|Number of pages||7|
|Journal||World Health Statistics Quarterly|
|State||Published - Jan 1 1988|
ASJC Scopus subject areas
- Public Health, Environmental and Occupational Health